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Beacons and sounders: it's all a matter of 'good practice'

09 July 2012

The Machinery Directive 2006/42/EC urges machine builders to undertake a thorough safety analysis of the systems that monitor and control the operation of their machines. While the 'dos' and 'don'ts' are well defined in the Directive for many aspects of machine safety, guidelines for the provision of visual and audible warning indicators are more vague; there is ‘guidance’ but little in the way of ‘you must....’. In Simon Adams’ view, it is more a case of applying 'good practice'.

Visible and audible warning lights on a machine or workstation generally indicate a change in status and may also warn of an error in machine operation or a malfunction. In any event, staff working in the vicinity of equipment displaying warning lights need to be aware of the change in machine status indicated by them, and take such steps as their operating procedures require.

So, how can a supplier of visible and audible warning systems contribute towards ensuring that ‘good practice’ is achieved in the workplace? A starting point is the risk assessment; once the risks have been identified, the next stage is to reduce them to an acceptable level. The general rules are: if there’s a risk, eliminate it; if you can’t eliminate it, guard it, and if you can’t guard it, warn about it.

One of the most dangerous phases of any machine operation is start-up. When you press the ‘go’ button, the last thing you want it to do is to start the machine. It must first initiate a procedure to check for safety Interlocks and self-test routines to ensure it is in an appropriate mode for start-up, with guards closed and so on. It might be common practice to monitor danger zones with light curtains and similar technology, but these systems can be overridden by operators; unless you can see the danger zone is clear, can you be sure it is safe to start?

The Directive tells us that “machinery must not start up unexpectedly”. It’s difficult to define what “unexpectedly” means in this context, so let’s turn it around, making sure that anyone in the vicinity of a machine will expect an audible and/or visual warning as part of its start-up sequence.

Now we’re all familiar with the concept of traffic lights and will intuitively understand that a red light is something that requires a certain defined response. So it is with visible and audible warning systems. The characteristics of the signal, the brightness of the beacon and loudness of the sounder need to be appropriate to the machine and its environment. And, just as importantly, make sure the paperwork’s done and the meaning of the signals is included in the operating manuals.

WERMA is a leading European manufacturer of visible and audible warning systems and accessories, including signal towers, beacons, sirens, buzzers and horns in a wide range of colours, light pictures and sound emission levels. The company can provide a solution to virtually any machine status and safety monitoring problem.

Earlier this year, the company joined forces with five other manufacturers of safety related equipment (Pilz, Festo, Troax, Fortress Interlocks and UK Engineering) to form the Machinery Safety Alliance, the main purpose of which is to provide expert and impartial advice on machine safety related issues via regular seminars and the Internet. Visit the website for more information.

Simon Adams is managing director of WERMA UK

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